Cut-off values for predictors associated with outcome in dairy calves suffering from neonatal calf diarrhea. A retrospective study of 605 cases

The considerable impact of neonatal calf diarrhea (NCD) on animal health and productivity prompted us to review the clinical and laboratory data in diarrheic calves presented to a referral institution. This study aimed to identify the major predictors associated with outcome in affected calves undergoing a standard therapy protocol and to evaluate the diagnostic performance of significant predictors for identifying the corresponding optimal cut-off values associated with outcome. Signalment, clinical signs, serum total protein (STP) concentration measured with an optical refractometer, venous blood gas analysis, treatment, and outcome were reviewed in 605 Holstein Friesian calves with uncomplicated NCD over 12 years. Calves were treated according to the severity of the clinical status with 3 standard fluid therapy regimens. After therapy, 414 calves were discharged in a healthy state, and 191 died. A multivariable logistic regression model indicated that survival was associated with STP concentration (odds ratio: 2.74; 95% confidence interval: 2.10-3.56; P < 0.001), rectal temperature (odds ratio: 1.22; 95% confidence interval: 1.03-1.44; P = 0.024) and blood pH (odds ratio: 7.49; 95% confidence interval: 1.33-42.18; P < 0.022). Receiver operating characteristic analysis showed that the optimal cut-off value of STP for predicting positive outcome was >50 g/L, associated with a sensitivity (Se) of 71.2%, a specificity (Sp) of 71.3%, a positive predictive value (PPV) of 84.5%, and a negative predictive value (NPV) of 53.2%. Optimal cut-off values for predicting positive outcome were rectal temperature >38.3°C (Se=61.6%, Sp=55.5%, PPV=74.9%, NPV=40.1%) and blood pH >7.12 (Se=68.7%, Sp=42.4%, PPV=71.4%, NPV=39.3%), despite the poor accuracy of these predictors according to the area under the curve (AUC). When association between predictors and outcome was analyzed split according to treatment regimens, the only predictor associated with outcome was STP concentration. Collectively, these findings suggest that STP is effective as a positive prognostic factor for diarrheic calves, with an STP concentration >50 g/L associated with a higher probability of survival. Additionally, our findings suggest that high STP may influence calf health during NCD.